Public API for programmatic registration of Taglet?

[Jonathan Gibbons]

FYI, the Taglet.init issue has been addressed.

https://bugs.openjdk.java.net/browse/JDK-8201817

The issue about programmatic registration (addCustomTag) is still under 
investigation.

-- Jon


On 4/18/18 9:08 AM, Martin Desruisseaux wrote:
>
> Hello
>
> I'm trying to write an extension of the standard doclet together with 
> custom taglets in the same JAR file. The custom taglets and doclet 
> need to share information. But I faced the following difficulties:
>
> When the Taglet.init​(DocletEnvironment,Doclet) method is invoked, the 
> doclet argument given by the caller is the internal HtmlDoclet wrapped 
> by StandardDoclet, not my custom StandardDoclet subtype. So I can not 
> get my doclet and taglet in touch that way.
>
> The lazy workaround - shared static fields - does not work because the 
> taglet is loaded in a different class loader than the doclet. So even 
> if I change a static field value from the taglet, the doclet never see 
> that change. This is not a multi-threading issue; I tested with 
> volatile static field. I also verified that the class loaders for the 
> same class were different depending on whether the class of my JAR 
> file is accessed from the doclet or from the taglet.
>
> I tried to wrap DocletEnvironment in order to return a customised 
> ForwardingJavaFileManager, in an attempt to control which ClassLoader 
> is used for loading the taglet. But the standard doclet does not seem 
> to accept customized DocletEnvironment, as suggested by the error that 
> I got:
>
>     java.lang.ClassCastException: org.opengis.tools.doclet.ForwardingDocletEnvironment cannot be cast to jdk.javadoc/jdk.javadoc.internal.tool.DocEnvImpl
>              at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.WorkArounds.<init>(WorkArounds.java:101)
>              at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:108)
>              at jdk.javadoc/jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:72)
>              (...snip...)
>
> The jdk.javadoc.internal.doclets.toolkit.taglets.TagletManager class 
> has public void addCustomTag(Taglet) method which seems perfect for my 
> need, but I found no public API for accessing this functionality.
>
> Is there a public way for a doclet to know its registered taglets, or 
> any other workaround that I may have missed? If not, would the 
> following evolution of Javadoc tools be possible?
>
>   * When extending the StandardDoclet, the doclet given in
>     Taglet.init(...) method should be the user StandardDoclet instance
>     instead than the JDK internal HtmlDoclet.
>   * Alternatively, a public API for addCustomTag(…) functionality
>     would also work.
>
> Regards,
>
>     Martin
>
>

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